Battery

Ageing is a one-way process.

10% drop in 12 months is OK.

Have Apple fit a new one at 80%

iPhone Battery and Performance - Apple Support

zahid25 Said:

"Battery: Within 1 year my iPhone 12 pro’s battery health decrease now it’s 90% will please help me to increase its battery health?"

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Knowing is Not an Option:

Unfortunately, there is no way to increase Battery Health, nor can you determine why, as it decreases on its own.